1. Field of the Invention
The present invention relates to a personal computer having a plurality of bootstrap devices including a hard disk drive detachable to the personal computer.
2. Description of the Related Art
Compact, light-weight and low-cost personal computers have been developed. Such a personal computer is equipped with minimum functions and any other functions which are optionally provided. Some personal computers have a single floppy disk drive, others have dual floppy disk drives, and others have a single floppy disk drive and a hard disk drive. In order to set up a system, a boot process is performed. More specifically, a CPU first reads the boot record of the floppy disk drive (FDD). If the CPU cannot read the boot record of the FDD, then it reads the boot record of another FDD, if present, or reads the boot record of the hard disk drive (HDD) if the second FDD is not present. If the CPU can read the boot record of the FDD or the HDD, then it loads an operating system program stored in FDD or HDD. Thus, the system is set up.
As described above, in the prior art, the boot priority is preliminarily fixed.
Recently, a type of personal computer having a detachable hard disk pack has been developed in order to further improve the portability. This type of personal computer is provided with a disk operating system (DOS) read only memory (ROM) (hereinafter referred to as DOS-ROM). The DOS-ROM has a similar format as the hard disk drive and stores a DOS file. More specifically, if the hard disk drive is not attached to the computer's main body, the DOS-ROM serves as the hard disk drive. The device number "80H" is assigned to the HDD and the device number "81H" may be assigned to the DOS-ROM in accordance with the specification of the industry standard interface.
However, if the device number "80H" is designated while the HDD is not attached and a device having the device number "81H" is present, the boot process cannot be performed due to the constraint of the industry standard DOS.